This project is designed to study the possible intrarenal actions of angiotensin II and other hormones which may be involved in the control of intrarenal blood flow and tubular sodium handling. Using inhibitors of angiotensin I converting enzyme, inhibitors of prostaglandin synthesis and competitive inhibitors of angiotensin II, changes in renal function including intrarenal blood flow distribution will be determined. Total renal blood flow is determined using an electromagnetic flow meter. Inulin clearance is used as are estimates of glomerular filtration rate. Intrarenal blood flow distribution is measured using radioactive microspheres. Sodium excretion is calculated by standard techniques. By determining the effects of various inhibitory drugs alone and in combination, we hope to further clarify the mechanisms involved in the control of intrarenal hemodynamics.